Fluid-structure interactions in Francis turbines: A perspective review

Trivedi, Chirag; Cervantes, Michel

doi:10.1016/j.rser.2016.09.121

Cited by 109 publications

(57 citation statements)

References 100 publications

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“…This Francis Turbine has a specific speed (n s ) of 46 (further information about hydraulic turbines specific speed can be found in [12]) and a rated power of 444 MW. This study is part of the collaborative European Project Hyperbole (FP7-ENERGY-2013-1) [13].…”

Section: Description Of the Selected Turbinementioning

confidence: 99%

Power Swing Generated in Francis Turbines by Part Load and Overload Instabilities

et al. 2017

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Abstract:Hydropower plays a key role in the actual energy market due to its fast response and regulation capacity. In that way, hydraulic turbines are increasingly demanded to work at off-design conditions, where complex flow patterns and cavitation appear, especially in Francis turbines. The draft tube cavitation surge is a hydraulic phenomenon that appears in Francis turbines below and above its Best Efficiency Point (BEP). It is a low frequency phenomenon consisting of a vortex rope in the runner outlet and draft tube, which can become unstable when its frequency coincides with a natural frequency of the hydraulic circuit. At this situation, the output power can significantly swing, endangering the electrical grid stability. This study is focused on the detection of these instabilities in Francis turbines and their relationship with the output power swings. To do so, extensive experimental tests for different operating conditions have been carried out in a large prototype Francis turbine (444 MW of rated power) within the frame of the European Project Hyperbole (FP7-ENERGY-2013-1). Several sensors have been installed in the hydraulic circuit (pressure sensors in the draft tube, spiral casing, and penstock), in the rotating and static structures (vibration sensors, proximity probes, and strain gauges in the runner and in the shaft), as well as in the electrical side (output power, intensity, and voltage). Moreover, a numerical Finite Element Method (FEM) has been also used to relate the hydraulic excitation with the output power swing.

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Section: Description Of the Selected Turbinementioning

confidence: 99%

Power Swing Generated in Francis Turbines by Part Load and Overload Instabilities

et al. 2017

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“…In order to avoid damages provoked by vibration resonances and material fatigues due to hydraulic excitations [4,5], the structural behavior of the turbine runner has to be carefully investigated during the design phase. Extensive research has been carried out to measure and characterize the vibrations and dynamic stresses induced by pressure fluctuations in Francis turbines [6,7] and pump-turbines [8,9].…”

Section: Introductionmentioning

confidence: 99%

Added Mass Effects on a Francis Turbine Runner with Attached Blade Cavitation

Huang

Escaler

2019

Fluids

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To have a safe structural design, an analysis of the dynamic behavior of a Francis turbine runner with consideration of the added mass effects of surrounding water is necessary during design phase. Both in design and at off-design operations, large-scale forms of attached cavitation may appear on runner blades and can change the added mass effects of the surrounding fluid in relation to a single water domain. Consequently, a numerical investigation of the modal response of a Francis runner has been carried out by reproducing the presence of various sizes of leading edge cavitation (LEC) and trailing edge cavitation (TEC). The fluid–structure interaction problem has been solved by means of an acoustic-structural coupling method. The calculated added mass effects with cavitation have been compared with those corresponding to the pure water condition without cavitation. Firstly, a single blade has been investigated to evaluate the level of significance for the proposed cavity shapes and dimensions. Afterwards, based on the results obtained, the complete runner structure has been considered, factoring in similar cavity shapes and locations. The results prove that significant added mass effects are induced on the entire runner by the attached cavitation that increase the natural frequencies of the first modes. Moreover, the added mass effects increase with cavity size and amplitude of blade deformation below the cavity.

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“…It can produce periodic forces on the object causing periodic vibration, especially when the vortex shedding frequency coincides with one of the natural frequencies of the vane, threatening resonance occurs, which will lead to more violent vibration and potentially initiating cracks [3,4]. The resonance induced by the Kármán vortex not only disturbs the downstream flow, resulting efficiency reduction and leading to channel vortex, but also causes serious damage to the unit components [5,6]. Therefore, it is very important to carry out theoretical research and an engineering investigation of the Kármán vortex resonance in a large-scale turbine, which is very meaningful for the antivibration and anticracking of a hydropower unit.…”

Section: Introductionmentioning

confidence: 99%

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

et al. 2017

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Abstract:In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV) and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM) is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane's trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM) and particle swarm optimization (PSO) is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD) simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry.

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Fluid-structure interactions in Francis turbines: A perspective review

Cited by 109 publications

References 100 publications

Power Swing Generated in Francis Turbines by Part Load and Overload Instabilities

Power Swing Generated in Francis Turbines by Part Load and Overload Instabilities

Added Mass Effects on a Francis Turbine Runner with Attached Blade Cavitation

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

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